What version have I installed
Blender 2.9x
There are four locations that show the version in varying level of detail.
Splash screen


Status Bar

About Blender


Export System Information

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= Blender 2.91.0 Alpha System Information =
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Blender:
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version: 2.91.0 Alpha, branch: master, commit date: 2020-08-06 17:52, hash: 9a1ff4445b98, type: 
build date: 2020-08-06, 21:59:05


Blender 2.8x
There are three locations that show the version in varying level of detail.
Splash screen with the name of the release


Status bar with the version number


Help &gt; Save System Info detailed information including the commit hash

Excerpt from the system-info.txt
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= Blender 2.80 (sub 75) System Information =
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Blender:
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version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: f6cb5f54494e, type: 
build date: 2019-07-29, 09:44 AM